Running without a thermostat!
02-23-2003, 11:29 AM
#17
Burning Brakes
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Ell,
Thank you - I learnt it the 'the hard way' and that's my hobby
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
Ups! - Two times - How to delete?
Thank you - I learnt it the 'the hard way' and that's my hobby
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
Ups! - Two times - How to delete?
02-23-2003, 12:19 PM
#18
Racer
Mark, thats great info your sharing. I thought about doing that once to keep the motor running cooler in the summer time when the weather is in the 100+ range.
Why do you think it worked loss?
Thanks for proving to me it will work!
Why do you think it worked loss?
Thanks for proving to me it will work!
02-23-2003, 12:42 PM
#19
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OK -
The plug was in the small inner opening where the, as described by Eric, special seal goes.
Max - This car came out of Miami...so - it obviously does work!
The plug was in the small inner opening where the, as described by Eric, special seal goes.
Max - This car came out of Miami...so - it obviously does work!
02-23-2003, 12:52 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Erik - Denmark:
The logic is good enough
1. When the thermostat is cold and closed the cooling water is circulating in the block (your item 2)
2. When the thermostat is hot, it open and when the thermostat is open it close the internal circulation and force the cooling water from the block to go via the radiator back to the block
(Your item 2)
Remember on your 1985 model you have a seat rubber gasket (not a O-ring but a special circular ring to be pressed into the seat behind the thermostat
This started with the 1984 (S2 model)to prevent overheating due to corrosion in the alu-seat
<img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" /> [/QB]</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Dangit - the more I think about this, the more confused I get...help me out here, Erik...
It seems as tho this is backwards from 'normal' cars. If the stat is closed all the time, simulating coolant in block below ~175...what is going on with the coolant in the radiator...and WHY doesn't he block overheat????
Maybe if someone could point me to a coolant flow diagram in the Manual or PET (couldn't find anyting there) OR just draw me one...it would help A LOT!! (Guess I'm just a visual guy!)
The logic is good enough
1. When the thermostat is cold and closed the cooling water is circulating in the block (your item 2)
2. When the thermostat is hot, it open and when the thermostat is open it close the internal circulation and force the cooling water from the block to go via the radiator back to the block
(Your item 2)
Remember on your 1985 model you have a seat rubber gasket (not a O-ring but a special circular ring to be pressed into the seat behind the thermostat
This started with the 1984 (S2 model)to prevent overheating due to corrosion in the alu-seat
<img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" /> [/QB]</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Dangit - the more I think about this, the more confused I get...help me out here, Erik...
It seems as tho this is backwards from 'normal' cars. If the stat is closed all the time, simulating coolant in block below ~175...what is going on with the coolant in the radiator...and WHY doesn't he block overheat????
Maybe if someone could point me to a coolant flow diagram in the Manual or PET (couldn't find anyting there) OR just draw me one...it would help A LOT!! (Guess I'm just a visual guy!)
02-23-2003, 01:09 PM
#21
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The block doesn't overheat because once the coolant temp gets about 75 or 83 degrees C, the T-stat will open which closes the bypass chamber and routes the coolant to the radiator.
With the plug in the smaller inner opening what you had was effectively an open T-stat all the time. Your coolant was being pumped into the radiator at all times, this is why your car ran so cool.
With the plug in the smaller inner opening what you had was effectively an open T-stat all the time. Your coolant was being pumped into the radiator at all times, this is why your car ran so cool.
02-23-2003, 01:10 PM
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Mark,
The thermostat acts like a three-way valve and opens one passage (through the thermostat) when the car heats up which opens flow to the radiator, *and* closes another passage (part of the housing) which blocks the recirculating flow within the block.
“Open” and “closed” are a matter of semantics here – the thermostat is diverting the coolant flow from the water pump in two directions. The thermostat unit itself opens in the traditional sense; if you drop it in a pot of boiling water, a thingy moves and opens a passage which was previously closed. But when installed in the vehicle, when it opens its own passage, the thingy moves into a passage which is part of the manifold where it sits & closes that one. When it is cold, the thermostat diverts the coolant flow through that other passage in a recirculating path through the engine, to avoid hot spots that might develop if the coolant were stagnant. When it heats up, the thermostat diverts the coolant to the radiator and occludes the recirculation path. When the radiator is subject to cold, high velocity air, the thermostat seeks a balance between the two paths in order to maintain a *high enough* coolant temperature.
The thermostat acts like a three-way valve and opens one passage (through the thermostat) when the car heats up which opens flow to the radiator, *and* closes another passage (part of the housing) which blocks the recirculating flow within the block.
“Open” and “closed” are a matter of semantics here – the thermostat is diverting the coolant flow from the water pump in two directions. The thermostat unit itself opens in the traditional sense; if you drop it in a pot of boiling water, a thingy moves and opens a passage which was previously closed. But when installed in the vehicle, when it opens its own passage, the thingy moves into a passage which is part of the manifold where it sits & closes that one. When it is cold, the thermostat diverts the coolant flow through that other passage in a recirculating path through the engine, to avoid hot spots that might develop if the coolant were stagnant. When it heats up, the thermostat diverts the coolant to the radiator and occludes the recirculation path. When the radiator is subject to cold, high velocity air, the thermostat seeks a balance between the two paths in order to maintain a *high enough* coolant temperature.
02-23-2003, 01:23 PM
#23
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kblair and Old/new - Thanks - NOW I understand.
When I originally posted about running cool all the time, it generated MUCH discussion on t-stats.
Arguements over whether you could run without a stat...some said YES...others were adamant that you can't and that it would overheat..
GUESS WHAT - THEY WERE BOTH RIGHT (ASTERISK)!
You CAN run without a stat - provided you plug the smaller inner opening! (The asterisk from above!)
If you run WITHOUT a stat (or - your plug comes out of the inner opening!) - the engine will overheat in a matter of MINUTES!
When I originally posted about running cool all the time, it generated MUCH discussion on t-stats.
Arguements over whether you could run without a stat...some said YES...others were adamant that you can't and that it would overheat..
GUESS WHAT - THEY WERE BOTH RIGHT (ASTERISK)!
You CAN run without a stat - provided you plug the smaller inner opening! (The asterisk from above!)
If you run WITHOUT a stat (or - your plug comes out of the inner opening!) - the engine will overheat in a matter of MINUTES!
02-23-2003, 03:20 PM
#24
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Mark,
As KBlair and Old & New said, it work like a three way valve, but with one exception:
I do not have a diagram, but I can try to explain it:
The cooling water comes from the water pump, who has two equal exits, one for each cylinder banks - at cylinder # 4 and 8 it pass via holes in the head gaskets to the two cylinder heads back to the thermostat house - Here is a y way back to the pump, one direct (easy), and one (longer and more difficult) via the radiator
- When cold, both Y ways are open and the water takes the direct (easy) way back to the pump
- When warm the direct way is closed and the water is forced to go (the longer and more difficult way) via the radiator
Remember: water is lazy, and always runs the easiest way.
I.e. when driving, the thermostat open and close the 'easy way' according to the actual need for cooling - That also means that's important that the seat for closing the 'easy way' is intact, and that's the reason for the rubber sealing after 1984. For cars from before 1984 check the alu-seat, or change your thermostat housing - According the the original spare parts list Porsche has exchange service from old to new houses - I do not know if that still exciting - if not, that's possible to machine the the old house for installing the rubber seal - If/when I repair an engine from before 1984, I will certainly install the rubber seal
As KBlair and Old & New said, it work like a three way valve, but with one exception:
I do not have a diagram, but I can try to explain it:
The cooling water comes from the water pump, who has two equal exits, one for each cylinder banks - at cylinder # 4 and 8 it pass via holes in the head gaskets to the two cylinder heads back to the thermostat house - Here is a y way back to the pump, one direct (easy), and one (longer and more difficult) via the radiator
- When cold, both Y ways are open and the water takes the direct (easy) way back to the pump
- When warm the direct way is closed and the water is forced to go (the longer and more difficult way) via the radiator
Remember: water is lazy, and always runs the easiest way.
I.e. when driving, the thermostat open and close the 'easy way' according to the actual need for cooling - That also means that's important that the seat for closing the 'easy way' is intact, and that's the reason for the rubber sealing after 1984. For cars from before 1984 check the alu-seat, or change your thermostat housing - According the the original spare parts list Porsche has exchange service from old to new houses - I do not know if that still exciting - if not, that's possible to machine the the old house for installing the rubber seal - If/when I repair an engine from before 1984, I will certainly install the rubber seal
02-24-2003, 01:19 AM
#25
One last thing.
There was another tidbit that Jay and or Dennis passed on to me:
The thermostat housing will leak without a thermostat.
True or not?
You should be able to determine this while you are tinkering.
Also,
I believe Dennis said the 944 (or was that 944 turbo?)Thermostat fits and is available at a number of Auto parts stores.
John S.
There was another tidbit that Jay and or Dennis passed on to me:
The thermostat housing will leak without a thermostat.
True or not?
You should be able to determine this while you are tinkering.
Also,
I believe Dennis said the 944 (or was that 944 turbo?)Thermostat fits and is available at a number of Auto parts stores.
John S.
02-24-2003, 09:02 AM
#26
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John - I had NO leakage from the housing...of course - without the plug, it would probably leak from the pressure created from the heat when she boils over!!
02-27-2003, 10:38 PM
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UPDATE - I ordered the seat gasket, thermostat and o-ring from 928 Specialists (got the usual great service and shipped as promised)...Put it all back together (PROPERLY!!!) She runs and cools/heats great! Whereas the needle used to stay on the bottom line of the gauge (at least until that little 'butt plug' -as my wrench calls it- fell out!). Now she goes to the next line...or just slightly above and just sits there! PLUS - I now am able to get some SERIOUS warmth out of my heater!
(Now...fishing the seat gasket out with a coat hanger (TWICE!) <img border="0" title="" alt="[Eek!]" src="eek.gif" /> when it fell down is another lesson - PLUG THAT PUPPY WITH A RAG!)
(Now...fishing the seat gasket out with a coat hanger (TWICE!) <img border="0" title="" alt="[Eek!]" src="eek.gif" /> when it fell down is another lesson - PLUG THAT PUPPY WITH A RAG!)
02-28-2003, 12:01 AM
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Oh oh.... <img border="0" title="" alt="[Eek!]" src="eek.gif" />
I just replaced the thermostat manifold seals because the lower one was oozing. And guess what.... there was nothing behind my thermostat except a bunch of corrosion in that smaller orifice. <img border="0" alt="[crying]" title="" src="graemlins/crying.gif" /> IF there had been a rubber seal back there, do I need to look for it somewhere in the engine?
I guess it all comes off again. <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" />
The PET does not show this area well.
Looking at the 928 Int'l website, they list:
Thermostat seal '84-95
Thermostat o-ring
Crossover seal '85-95
On disassembly, I found only one piece of rubber, and it was like a flat o-ring with a groove along the inside edge that fit the edge of the thermostat, creating a rubber seal on both surfaces of the periphery of the thermostat. I take it that this would be the "Thermostat seal '84-95". Is the "Crossver seal '85-95" the thing that goes into the smaller orifice? Then where does that "Thermostat O-ring" go?
I just replaced the thermostat manifold seals because the lower one was oozing. And guess what.... there was nothing behind my thermostat except a bunch of corrosion in that smaller orifice. <img border="0" alt="[crying]" title="" src="graemlins/crying.gif" /> IF there had been a rubber seal back there, do I need to look for it somewhere in the engine?
I guess it all comes off again. <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" />
The PET does not show this area well.
Looking at the 928 Int'l website, they list:
Thermostat seal '84-95
Thermostat o-ring
Crossover seal '85-95
On disassembly, I found only one piece of rubber, and it was like a flat o-ring with a groove along the inside edge that fit the edge of the thermostat, creating a rubber seal on both surfaces of the periphery of the thermostat. I take it that this would be the "Thermostat seal '84-95". Is the "Crossver seal '85-95" the thing that goes into the smaller orifice? Then where does that "Thermostat O-ring" go?
